Git branching lets developers work on new features, fixes, and experiments without changing the main version of a project right away. This cheat sheet helps students understand how branches split, move, and come back together. It is useful for class coding projects, team collaboration, and keeping a clean project history.
Knowing merge strategies also helps students avoid lost work and confusing conflicts.
Key Facts
- Create and switch to a new branch with git switch -c branch-name, which makes a branch pointer and checks it out.
- List local branches with git branch, and the currently checked-out branch is marked with an asterisk.
- A fast-forward merge happens when the target branch has no new commits, so Git simply moves the branch pointer forward.
- A three-way merge uses the two branch tips and their common ancestor to create a new merge commit.
- Rebase with git rebase main rewrites commits from the current branch so they appear after the latest commit on main.
- Resolve a merge conflict by editing the conflicted file, running git add file-name, then completing the merge with git commit or git rebase --continue.
- Pull updates safely with git pull, which is usually equivalent to git fetch followed by git merge for the current tracking branch.
- Delete a merged local branch with git branch -d branch-name, but use git branch -D branch-name only when you intentionally want to force deletion.
Vocabulary
- Branch
- A branch is a movable pointer to a commit that lets you work on a separate line of development.
- Commit
- A commit is a saved snapshot of project changes with an ID, author, message, and link to previous commits.
- Merge
- A merge combines changes from one branch into another branch.
- Fast-forward
- A fast-forward is a merge where Git only moves the target branch pointer forward because there are no separate commits to combine.
- Rebase
- A rebase reapplies commits from one branch onto the tip of another branch to create a straighter history.
- Merge conflict
- A merge conflict happens when Git cannot automatically decide how to combine competing changes in the same part of a file.
Common Mistakes to Avoid
- Merging the wrong direction, such as merging main into a feature branch when the goal is to finish the feature, is wrong because it does not place the feature work onto main.
- Using git branch branch-name and expecting to switch branches is wrong because git branch only creates or lists branches unless paired with a checkout or switch command.
- Rebasing shared commits is risky because rewriting history can confuse teammates who already based work on the old commits.
- Ignoring conflict markers like <<<<<<<, =======, and >>>>>>> is wrong because those markers are not valid final code and must be edited out manually.
- Forcing branch deletion with git branch -D without checking the work is wrong because unmerged commits may become hard to find or recover.
Practice Questions
- 1 You are on main and need to start a feature called login-form. What command creates the branch and switches to it in one step?
- 2 A branch feature has 4 commits after splitting from main, and main has 0 new commits. What merge strategy will Git likely use when merging feature into main?
- 3 A branch feature has 3 commits after splitting from main, and main has 2 new commits after the split. Why is this not a fast-forward merge?
- 4 A teammate suggests using rebase on a branch that has already been pushed and used by others. Explain why a merge may be safer for collaboration.